For determination of suitable process conditions at drying of European beechwood (Fagus sylvatica L.) the unidirectional drying kinetics, with an emphasis of free water removal was researched. We used radially oriented sapwood specimens, having thickness from 6 mm to 24 mm (ΔL = 6 mm). Series of conventional drying processes were carried out in the laboratory tunnel drier at constant climate (T = 30 °C, φ = 85 %) with various air velocities from 0.6 m/s to 7.6 m/s. During the drying, moisture content, moisture gradient and moisture flow were gravimetrically determined at successive time intervals. Drying rate generally increased by rising of the air velocity and decreased by increasing of wood thickness. Relatively constant drying rate was present at thinner specimens (≤ 12 mm) in a short time interval of the initial stage of the process, when low air velocity was used (≤ 2.5 m/s). Increasing of the air velocity (> 2.5 m/s) lead to early irreversible reduction of initial moisture flow and to the transition into the period of significantly falling drying rate, where the internal mass resistance predominated. The diffusion barrier was induced at too fast free water removal which controlled further drying rate and significantly prolonged the process in continuation
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